Reactive oxygen species (ROS) and reactive nitrogen species (RNS) include oxygen ions, free radicals, peroxides, and the like, which are highly reactive due to the presence of unpaired valence shell electrons. Several predominant ROS/NOS in the environment include peroxyl radicals, hydroxyl radicals, superoxide, singlet oxygen, and peroxynitrile. The human skin is highly susceptible to such ROS/NOS in the environment and exposure to ROS/NOS is known to produce detrimental effects to human skin. Antioxidants are ROS/NOS scavengers which function by offering easy electron targets for ROS/NOS. By absorbing ROS/NOS, antioxidants provide a defense against ROS/NOS in the environment.
Manufacturers are now beginning to add antioxidants to skin care products, e.g., cosmetics, sun tanning oils, sun screen products, and the like, as a defense to the damaging predominant ROS/NOS in the environment. As a result, manufacturers of skin care products, and the consumers that use them, often like to know the antioxidant capacity of a particular skin care product. Because skin care products are often manufactured with unique and proprietary chemical formulations and are applied directly to the surface of the skin, the manufacturer and/or consumer needs to know the antioxidant capacity of the skin care product as it exists in its manufactured form and as it is applied to the skin.
Conventional methods for assaying the antioxidant capacity of a sample, such as those disclosed in U.S. Pat. No. 7,132,296 by one or more of the inventors hereof, incorporated by reference herein, rely on preparing a sample for testing in which by various chemicals, solubility enhancing compounds, extraction solutions, and the like are added to the sample. Such a technique typically alters or destroys the proprietary chemical formulation of the skin care product and thus does not provide a true measurement of the antioxidant of the skin care product as it is manufactured and as it is applied to the skin. Moreover, conventional methods for measuring the antioxidant capacity of a sample typically utilize a single probe which is sensitive to only one type of ROS/NOS. Thus, these conventional methods can only provide the antioxidant capacity for a one type of ROS/NOS.
Moreover, one theory on aging indicates the human skin ages because the cells in the skin accumulate ROS/NOS over time. Thus, there is a need for a panel of assays, or an anti-aging protection factor score, which can provide a true measurement of the antioxidant capacity of a skin care product for the predominant ROS/NOS in the environment.